1. The state of being dichromatic (1).
2. The abnormality of color vision in which only two of the three retinal cone pigments are present, as in protanopia, deuteranopia, and tritanopia.
The information shown above for dichromatism is provided by Stedman's.
* Stedman's, part of Lippincott Williams & Wilkins, provide a comprehensive line of health-science publications for healthcare professionals and medical students.